As known, during a flight refueling phase, the refueling airplane and the refueled airplane should be positioned one behind the other and follow the same trajectory, at the same speed, and this throughout the whole refueling phase. Such a phase is particularly difficult, as the two airplanes should limit the relative position deviations according to the three axes throughout the whole refueling.
In order to limit such deviations, the two pilots should communicate together permanently and take into account the dynamics of their respective airplanes so as to coordinate to the best the relative trajectories of the two airplanes. Such a phase is therefore particularly demanding and nervously stressing for the pilots.
A simple means for limiting the relative deviations would be to implement a stabilized rectilinear flight, thus limiting the changes of attitude of the airplanes. However, as a refueling operation generally takes about twenty minutes, the distance covered in a straight line during this phase is often incompatible with the operational need (risk of entering an enemy area or flying too much apart from the operation theatre, for instance) so that such a solution is not used in principle.
Flight refueling operations are generally implemented along flight circuits having, most often, an oblong shape, with two parallel linear paths, laterally spaced apart one from the other and connected together at the ends thereof by circle arcs. Such a circuit therefore involves that the airplanes perform successively and alternately straight line flights, along linear paths, and stabilized turn flight, along circle arcs.
Such a straight line flight could be managed via the autopilot through a usual heading (or itinerary) holding mode, and a turn flight could be managed via the autopilot through a usual rolling (angle) holding mode or by the pilot manually.
If the refueling phase is managed manually, it is very probable that holding the heading and/or holding the rolling will not be perfectly respected, thus increasing the workload of the pilots, and including that of the refueled airplane.
On the other hand, if the heading and rolling holding phases are managed by the autopilot, the accuracy is improved upon such phases. However, in this case, if the pilot changes mode too late or too early, the trajectory will not be regular at the transitions, and as a result, changes of attitude of the refueling airplane will occur, that the pilot of the refueled airplane will have to compensate for.
The usual management of the transition between these two modes, and including of the rolling angle holding mode (with a not nil rolling angle) to a heading holding mode (with a nil rolling angle), is thus not completely satisfactory.
The usual management of the transition between these two modes, and including of the rolling angle holding mode (with a non-zero rolling angle) to a heading holding mode (with a zero rolling angle), is thus not completely satisfactory.
The present invention aims at remedying these drawbacks. It relates to a method for aiding the guidance of an airplane, for automatically aiding managing the transition from a current rolling angle holding mode, wherein the airplane flies with a constant (non-zero) rolling angle, to a following heading holding mode, wherein the airplane flies according to a constant heading with the wings being folded flat (that is with a zero rolling angle), in particular during a flight refueling phase.